A primary concern with any electronic device intended for implantation within the body is its power consumption as the power requirements dictate the ultimate size and operational lifetime of an implant. Most devices are powered by batteries that must be replaced to restore power, and surgical removal always involves risk and inconvenience to the patient. This undesirable feature greatly detracts from the benefits which may be gained from an implant device.
Transcutaneous transmission of information requires that the transmitter power be minimized. Over a period of time, fibrotic tissue may increase the density of the dermal cover and affect transmitted signal power requirements in light-based communication systems. In addition, the proximity and alignment of transmitter and external receiver may affect signal power requirements.
The type of information that is to be transmitted must also be considered. Information may be transmitted in a weak signal by making it highly redundant, but this will decrease the rate at which information may be acquired.
With certain variables of physiological interest, it may be necessary to monitor baseline of slow variations to observe long-term trends and also to monitor more rapid dynamic changes of interest for diagnostic purposes.
Past designs which use a transmitter power level based on a worst-case analysis of the above factors have a shorter lifetime than necessary.
The present invention provides a method whereby implant transmitter power is controlled externally, based upon the time resolution desired. Thus, the methodology of the invention maximizes the working lifetime of the implants and/or allows a reduction of size for the implanted device. These benefits of the present invention will extend the range of practicality to include implants which heretofore have not been justifiable.